Process for packing and drying solid wood and a plant for accomplishing same

ABSTRACT

A process for packing and drying solid wood, wherein the wood is treated with ammonia at elevated temperatures and under pressure, and simultaneously packed, thereby producing wood which features uniform density over its entire cross section. A plant for accomplishing the process of the invention, which helps simultaneously effect in a single chamber both ammonia treatment and forced packing.

United States Patent Berzin et al.

[ Mar. 7, 1972 [54] PR'DCESS FOR PACKING AND DRYING SOLID WOOD AND A PLANT FOR ACCOMPLIISHING SAME [72] Inventors: Gunard Valdemarovich Berzln, ulitsa Yaunsaules, l2; Arvid Yanovicl'i Kalnin, ulitsa Sverdlova, 8, kv. 3, both of Riga; Alexandr Fedorovicli Sushkov, Gogolevsky bulvar, 17, kv. 1, Moscow; Voldemar Petrovich Skrupsky, ulitsa Aptiekas, 13, kv. l; Andris Eduardovich Ziemelis, ulisa Stopinju, 50, kv. 1, both of Riga; Boris Fedorovich Soloviev, ulitsa Kalarash, 11, kv. 31, Ljubeitsy; Karl Mikhailovich Leeniex, ulitsa Parka, 4, Elgava; Vladimir Kirilovich Sovetin, ulitsa Moskovskaya, l, kv. 94, Ljubertsy; Yan Karlovieh Gulbis, ulitsa Lomonosova, l2, kv. 9; Yan Yanovich Dalbinsh, ulitsa Raunas, 45, kmpus 5, kv. 221, both of Riga; Bruno Andreevich Priede, ulitsa Rainya, 116, kv. 1, Jurmala; Karl Kristapovich Upman, ulitsa Fr. Engelsa, 20, kv. l0; Vitold losiiovich Muzhit, ulitsa Unias, 31, kv. 8; Yan Petrovich Junga, ulitsa Dzelzaves, l3, kv. l3; Ivar Arnoldovich Krogzem, ulitsa Talivalzha, 28, kv. 1;Zigurd Boleslavovieli Greitan, ulitsa Aglonas, 28, kv. 100; Karl Arturovich Rotsen, ulitsa N. Ostrovskogo, 2, kv. 2, all of Riga, USSR.

[22] Filed: May 7,1970

[21 Appl. No.: 35,502

[301 Forelgn Application Priority Data May 12, 1969 U.S.S.R ..1331274 [52 us. c1 ..34/1a.s, 34/165, 34/37, 34/145 s1 16:. c1. 26b7/00 [58] FieldolSeanch ..34/13.s, 16.5, 36,37, 14s

[56] References Cited UNITED STATES PATENTS 2,064,965 12/1936 Will ..34/l6.5

608,780 8/1898 1,328,507 1/1920 Fish 2,296,546 9/1942 Toney "34/37 FOREIGN PATENTS OR APPLICATIONS 684,915 4/1964 Canada "34/131;

Primary ExaminerCarroll B. Dority, Jr. Attorneywaters, Roditi, Schwartz & Nissen [57] ABSTRACT A process for packing and drying solid wood, wherein the wood is treated with ammonia at elevated temperatures and under pressure, and simultaneously packed, thereby producing wood which features uniform density over its entire cross section. A plant for accomplishing the process of the invention, which helps simultaneously effect in a single chamber both ammonia treatment and forced packing.

4 Claims, 1 DrawingFigure PROCESS FOR PACKING AND DRYING SOLID WOOD AND A PLANT FOlR ACCOMPLISHING SAME The present invention relates to processes for packing and drying solid wood and, more particularly, it relates to those of said processes in which packing and drying are effected by way of ammonia treatment and pressing.

It is known that for the purposes of drying and packing the wood used for the manufacture of various articles it is treated with ammonia under normal conditions or at elevated temperatures up to 100 C. and under pressure of up to 78 atm. in an atmosphere of ammonia, whereupon it is packed by pressing.

Up to now, such a treatment of solid wood was carried out in two stages: the wood was first treated with ammonia under the above-described conditions and then, with the ammonia treatment over and free ammonia volatilized from the wood, the wood was pressed.

For accomplishing this process, use was made mainly of the equipment intended for chemical treatment of wood, as well as diverse drying chambers and hydraulic presses or rolling mills; each of the groups of this equipment was used to service a respective stage of treating the wood.

When using the known process of treating solid wood, it is not always that the uniformity of its packing is attained. In case it is necessary to obtain the wood density below 1,200 kg./cu.m. or when treating blanks with a thickness exceeding 40 mm., the outer layers of the wood feature a much greater density than the inner ones. In some cases, when the blank is very thick, the density of middle layers increases after pressing but slightly as compared with the natural density. Such a nonuniform density has an adverse effect upon the article strength.

lt is an object of the present invention to insure the uniformity of packing in all of the above-described casesand provide a simplified technology of producing packed wood together with a full automation of this process, as well as to develop a plant that would provide for the possibility of combining the ammonia treatment and forced packing of wood in a single unit.

In the accomplishment of the foregoing object of the invention, when packing and drying solid wood by way of treating it with ammonia under pressure and subjecting it to forced packing, according to the invention, packing is carried out in the course of treating solid wood with ammonia, the gaseous medium in which the wood under treatment is placed being maintained in the state of forced circulation with a view to intensifying the process of wood dehydration in the course of packing.

Such a process of treating solid wood helps attain the uniformity of its packing in all the cases and, as shown by experiments, is advantageous in that it does not require predrying of wood as a separate operation, permitting an equally successful use of green wood. In addition, the proposed process helps considerably simplify the technology of treatment.

In accordance with the present invention, a plant for accomplishing the process for packing and drying solid wood in the course of combined treatment with ammonia at elevated temperatures and under pressure is essentially a hermetically sealed heated chamber accommodating thereinside a press table on which the wood being treated is placed, while the chamber walls incorporate at least one vertically extending power cylinder, whose free end inside the chamber carries a press plate, and a pipeline connected with an apparatus for the pressure feed of ammonia, as well as a fan serving to effect forced circulation of the gaseous medium inside the chamber. Such an arrangement makes for carrying out synchronous treatment and, in addition, improves the working conditions by precluding the entry of ammonia to the surrounding atmosphere.

Presented hereinbelow is the detailed description of an exemplary embodiment of the invention with reference to the accompanying drawing in which the sole FIGURE shows schematically a cross-sectional view of a plant for accomplishing the method according to the invention.

The plant for accomplishing combined treatment of wood with ammonia and forced packing in a single unit comprises a hermetically sealed chamber 1, accommodating thereinside a press table 2, mounted on a carriage 3 for convenience during charging and discharging of wood being treated. The carriage 3 is placed inside the chamber 1 on guides 4 and is brought inside the chamber 1 via an end face opening, said end face opening having a removable end face cover 5. Arranged inside the chamber 1 are also air heaters 6 for heating the internal space. The upper part of the chamber walls incorporates vertically extending hydraulic cylinders 7, the free ends of whose rods 8 protruding inside the chamber I, carry press plates 9. The hydraulic cylinders 7 are set to operation by a hydraulic drive station 10. Ammonia is supplied into the chamber 1 from a vessel 11 along a pipeline 12. A pipeline 13 serves for supplying live steam, if required. A pipeline 14 serves for dropping the pressure inside the chamber 1, and condensate is removed from the chamber 1 via a pipeline 15. Medium is sucked off from inside the chamber by means of a vacuum pump 16. A fan 17 provides for forced circulation of gaseous medium inside the chamber 1. For insuring the safety of the chamber operation, provision is made of a protection valve 18.

Prior to work, the end face cover 5 is opened and the carriage 3 is brought inside the chamber 1, the table 2 of the carriage carrying piles of blanks 19 separated from each other by spacers 20 of hard-to-deform material. The wood being treated can be of any species, including coniferous wood, featuring any degree of moisture content. Thereupon, the chamber 1 is tightly sealed with the cover 5, a valve 2] is opened and the vacuum pump 16 is actuated to create a required degree of vacuum inside the chamber after which the valve 21 is closed, a valve 22 on the pipeline 12 is opened and gaseous ammonia is fed inside the chamber 1 until a constant pressure of ammonia about 2 gauge atmospheres is reached inside the chamber. Pressure is controlled with the aid of a reducing valve 23. Simultaneously, a valve 24 is opened and steam is fed to the air heaters 6 which raise the temperature inside the chamber up to C. depending upon the conditions of drying.

Condensate from the air heaters is removed via pipeline 25.

After the chamber 1 is filled with ammonia, the valve 22 is closed, the fan 17 is switched on and the process of wood drying commences. Simultaneously with the fan 17, the hydraulic drive station 10 is actuated which sets to operation the hydraulic cylinders 7, and the process of forced packing of wood is effected together with the ammonia treatment. When so doing, the specific pressure of forced packing can be within the range of from 0.l to 12 kg.(force)/sq.cm., depending upon the required density of wood being treated. Condensate and moisture separated in the course of drying are removed as needed via the pipeline 15. For this purpose, a valve 26 is opened from time to time. If required to maintain the drying conditions, live steam is supplied to the chamber 1 via the pipeline 13 by opening a valve 27.

The process of combined treatment with ammonia and forced packing goes on for a period of up to 200 hours, depending upon the size of the wood blanks and initial moisture content. After the required period of time elapses, the heating of the chamber 1 is discontinued, the valve 21 is opened and, by actuating the vacuum pump 16, the gaseous medium is removed from the chamber 1. Following the removal of the gaseous medium, the vacuum pump 16 is disconnected, the valve 21 closed, and the pipeline 14 is opened with the aid ofa valve 28. After the plant together with the wood is cooled to ambient temperature, the fan 17 is switched off.

The hydraulic cylinders 7 perform a reverse stroke under the effect of the hydraulic drive station 10, the press plates 9 take the extreme upper position, and the wood is relieved of pressure. Thereupon, the treated wood is discharged. To this end, the end face cover 5 is opened and the carriage 3 with the treated wood is moved outside.

Further on, the operating cycle can be repeated as described hereinabove.

EXAMPLE 1 Blanks of green birch wood, 370X90 45 mm. in size are placed in the chamber 1 of the plant described hereinabove in piles as indicated in the specification. The chamber 1 is evacuated to a vacuum of 0.8 kg.(force)/sq.cm. according to a vacuum gauge, whereupon gaseous ammonia is fed inside the chamber 1 to a pressure of 1.0 gauge atmosphere, the heating and the fan 17 are actuated and the blanks are subjected to pressing with a specific pressure of 0.2 kg.(force)/sq.cm., this pressure being maintained to the end of the process. The chamber temperature is gradually raised to l l8i2 C. and the wood is held for 50 hours. After cooling the chamber together with the treated blanks, we obtain a material featuring a uniform density of 700-800 kg./cu.m. and moisture content of 3-5 percent.

In this example, as well as in all the subsequent ones, ammonia and accompanying water vapors are maintained in the course of treatment in a state of forced circulation with the aid of the fan 17 actuated simultaneously with the feed of ammonia at the beginning of heating. The above-specified pressure acting on the blanks is maintained to the end of the process of treatment. Likewise, the cooling of the chamber together with the treated blanks to ambient temperature takes place in all the cases.

EXAMPLE 2 Blanks of green birch wood sized 460X70X50 mm. are placed in the chamber 1 and put under vacuum as hereinbefore described. Gaseous ammonia is fed to the chamber 1 to a pressure of 1.5 gauge atmospheres. Thereupon, the blanks are subjected to a continually growing specific pressure of upto l.2 kg.(force)/sq.cm. The temperature is gradually raised to l 18i2 C. and the wood is held for 60 hours.

The treated blanks obtained feature a uniform density of 900-1 ,050 kg./cu.m. and a moisture content of 3-5 percent.

EXAMPLE 3 Blanks of birch wood sized 30OXl00X80 mm. and with an average moisture content of 70 percent are placed in the chamber 1 and put under vacuum as indicated above. Then, gaseous ammonia is supplied inside the chamber until the pressure thereinside is l.2 gauge atmospheres. Thereupon, with a gradual pressure increase the blanks are subjected to pressing at a specific pressure of 5 kg.(force)/sq.cm. The temperature is gradually raised to l l8+ C. and the wood is held for 70 hours. The treated blanks feature a uniform density of LOGO-1,200 kg./cu.m. and moisture content of 3-5 percent.

EXAMPLE 4 Blanks of green birch wood sized l,200 80 80 mm. are placed in the chamber 1 and put under vacuum as described above. Gaseous ammonia is supplied to the chamber 1 to attain thereinside a pressure of 2 gauge atmospheres. Thereupon, the blanks are subjected to pressing under a specific pressure growing gradually to 7 kg.(force)/sq.cm. The temperature is gradually raised to l l8+ -2 C. and the wood is held for hours. The treated blanks feature a density of l,l50-l,300 kg./cu.m.

EXAMPLE 5 Blanks of green birch wood sized 300 l00xl00 mm. are placed in the chamber 1 under vacuum as described above. Gaseous ammonia is fed to the chamber to a pressure of 0.5

gauge atmosphere Thereupon, the blanks are subjected to pressmg at a specific pressure continually growing up to 10 EXAMPLE 6 Blanks of green aspen wood sized 225X75X70 mm. are placed in the chamber 1 of the plant in a manner described above. The fan 17 is actuated, the temperature in the chamber is gradually brought to l l8+ C. and the blanks are held for 14 15 hours. After this period of time elapses, the moisture content of the blanks is on the average reduced to 30 percent. In the case of using predried 'wood there is no need of performing the above-mentioned operations. Thereupon, the temperature in the chamber 1 is brought down to 60fi C., gaseous ammonia is fed to the chamber until the pressure thereinside reaches 0.3 gauge atmosphere and, after 2-3 hours from the moment of ammonia introduction, the blanks are subjected to specific pressure of 7 kg.(force)/sq.cm..The temperature is gradually raised to l l8+ C. and the blanks are held for 25 hours. The resulting packed blanks feature a density of l,000l,l00 kg./cu.m. and moisture content of 3-5 percent.

Various alterations, improvements and modifications can be made in the proposed process according to the present invention, depending upon the species, dimensions and moisture content of the wood being treated, as well as upon the type of drying agent, without limiting the scope of the invention.

We claim:

1. A process for packing and drying solid wood comprising subjecting the wood to treatment with ammonia at elevated temperatures and under pressure and, simultaneously, to forced packing, the gaseous medium in which the wood under treatment is placed being maintained in the state of forced circulation.

2. A plant for packing and drying wood comprising: a hermetically sealed heated chamber including walls; at least one vertically extending power cylinder on one of said walls of said chamber; said power cylinder including a rod having a free end protruding inside said chamber; a press plate on said free end; a press table inside said chamber and adapted for the piling thereon of the wood being treated; a source of ammonia and an apparatus for the pressure feed of ammonia; a pipeline connecting said chamber with said apparatus for the pressure 

2. A plant for packing and drying wood comprising: a hermetically sealed heated chamber including walls; at least one vertically extending power cylinder on one of said walls of said chamber; said power cylinder including a rod having a free end protruding inside said chamber; a press plate on said free end; a press table inside said chamber and adapted for the piling thereon of the wood being treated; a source of ammonia and an apparatus for the pressure feed of ammonia; a pipeline connecting said chamber with said apparatus for the pressure feed of ammonia to the chamber; and a fan to effect forced circulation of the gaseous medium inside said chamber.
 3. A process as claimed in claim 1 wherein the pressure applied to the wood is about 0.1 to 12 kg./sq.cm.
 4. A process as claimed in claim 3 comprising placing the wood in a chamber, evacuating the chamber, feeding gaseous ammonia to the chamber, adding steam to the chamber, and actuating a fan in the chamber. 